The present invention is directed, in general, to semiconductor wafer processing and, more specifically, to an apparatus and method for improved cleaning of post-CMP (chemical/mechanical planarization) semiconductor wafers.
In the manufacture of integrated circuits (ICs), chemical/mechanical polishing (CMP) is used to provide smooth topographies of semiconductor wafer substrates on which the ICs are formed for subsequent lithography and material deposition. These CMP processes are well known within the IC fabrication industry.
One problem area associated with CMP is in the area of cleaning debris from the semiconductor wafers in the post-CMP environment. During CMP, at least some portions of the semiconductor wafer are abraded and may remain as debris on the wafer surfaces. This debris can damage the integrated circuits on the wafer and must be removed before subsequent processing. Conventional approaches include the use of open-cell plastic foam brushes, usually comprising polyvinyl alcohol, and a solvent to clean the wafers. Multiple brushes, often oriented to simultaneously clean both sides of the semiconductor wafer, are also used. The cleaning device is usually equipped with adjustments allowing the amount of contact and the pressure between the wafer and the brush to be controlled. A consistent cell or pore size within a single brush is generally achieved by foaming the plastic in the presence of a gas or liquid. Pore size directly affects the ability of the brush to remove particles from the semiconductor wafer. For example, a relatively small pore size is generally not very effective in removing larger particles from the semiconductor wafer; that is, the larger particles simply are not captured by small pores. Likewise, large pores have a tendency not to retain the smaller particles. The cleaning brushes used are generally those recommended by the equipment manufacturer without much further consideration. Therefore, using a single pore size for all of the brushes is effective for one range of particles and may miss a significant number of particles of other sizes.
A solvent is usually also used with the foam brushes to assist in the cleaning. This maintains a consistent level of resiliency in the foam. The brush may also be formed with ridges or knobs rather than a smooth surface. However, these variations in the brushes surface shape have not been shown to be significant in changing the cleaning effectiveness of the brush.
Accordingly, what is needed in the art is an apparatus and method of using such an apparatus that more effectively removes particulate debris remaining after CMP of a semiconductor wafer.
To address the above-discussed deficiencies of the prior art, the present invention provides in one embodiment a method of manufacturing an integrated circuit including cleaning a semiconductor wafer using a cleaning apparatus comprising a roller brush frame and roller brushes cooperatively supported within the roller brush frame and aligned to form a cleaning gradient; the cleaning gradient configured to remove particles of different sizes from an object to be cleaned. In another embodiment, each of the roller brushes has a different pore size associated therewith; the different pore sizes thereby forming the cleaning gradient.
In another embodiment, the roller brushes are a first set of roller brushes aligned to form a first cleaning plane and the cleaning apparatus further comprises a second set of roller brushes to form a second cleaning plane opposing the first cleaning plane. The second set of roller brushes have different pore sizes corresponding to the different pore sizes of the first set of roller brushes.
In an alternative embodiment, the first and second cleaning planes are substantially parallel and the first and second sets of roller brushes are aligned such that like pore sizes of the first and second sets of roller brushes oppose each other. In a further aspect, the roller brush frame further comprises axle apertures wherein the axle apertures are configured to permit independent adjustment of a distance between opposing roller brushes.
The roller brushes, in another embodiment, may comprise an open-celled brush material, such as an open-celled foamed plastic. In a specific aspect of this embodiment, the open-celled plastic is polyvinyl alcohol. In yet another embodiment, the roller brush frame further comprises load cells couplable to the roller brushes. In a further aspect, the load cells are adjustable load cells. In another embodiment, the cleaning apparatus further comprises a solvent dispenser coupled to the roller brush frame and configured to dispense a solvent to the roller brushes.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.